The prior art includes a variety of types of material spreaders. Conventional lawn fertilizer spreaders include a hopper and a finger agitator rotated by spreader wheels. More closely related to the invention apparatus are material spreaders adapted for heavy duty use in conjunction with the spreading of rock or other relatively hard and relatively large size particulate material during construction. A number of companies make material spreaders for evenly spreading a layer of topping material on the wet surface of spans of concrete. One such type conventional spreader mounts one or more hoppers on a bridge which spans the width of the concrete. The hoppers are driven back and forth on the bridge to spread the material. The bridge is mounted on wheels and is manually moved lengthwise of the span after each single, double or other number of passes of the hoppers depending on the depth of material being spread. The hopper drive mechanism for a spreader of this type is typically powered either electrically or pneumatically which requires either power cables or air lines to be fed back and forth across the concrete span being worked. Such arrangements inherently require additional support structure and expense for the added structure, cables and air lines.
In applicant's prior U.S. Pat. No. 4,555,200, entitled "Hydraulically Powered Material Spreader", the prior art is referred to and there is described a substantially improved material spreader in which the hoppers and spreader box are mounted on a support structure which is driven back and forth along an elevated path by means of gasoline engine powered hydraulic apparatus mounted on the same support structure. Heat, which accumulates in the hydraulic fluid during operation of the spreader, is dissipated by means of an improved reservoir/hopper-cooling arrangement which allows the heat to be absorbed both by a hopper wall and by the material being spread.
Experience with the type hydraulically-driven spreader described in U.S. Pat. No. 4,555,200 has proven that such spreader is well suited to spreading relatively uniform and relatively small size particles such as sand. However, the spreader taught in such patent as well as all other spreaders known to applicant failed to provide a spreader uniquely adapted for spreading large size rock and particularly with a hydraulic drive. A demand for spreading relatively large and non-uniform size rock, for example of 1/2" to 2" screen size, has arisen because of the trend towards using exposed aggregate in buildings and also because of the trend in forming patios, sidewalks, and floors with relatively large aesthetically attractive and longwearing rock surfaces.
The object of the invention described in applicant's copending application, Ser. No. 685,244, was that of providing a spreader more specifically adapted and useful in spreading relatively large and relatively non-uniform rock. The spreader of the copending application employs a pair of spring-loaded gates on opposite sides of a metal, hydraulically, motor-powered, rough-surfaced cylinder which rotates in a selected direction coordinated with the direction of travel of the hoppers on the bridge and which on each pass forces the rock out of the hoppers between one of the gates and the cylinder. The gates pivot back and forth according to the size rock passing through between the gate and the cylinder thus automatically accommodating both to the size rock being spread and to rock jams during which the hydraulic drive stalls without damage until cleared.
A relatively recent trend in the industry has been the practice of making concrete floors more light reflective by spreading light reflective, floor hardening material on wet concrete and allowing such material to become part of the finish surface both to harden the surface and reduce the electrical power lighting load. Such material is normally in a powder-like form. One such light reflective, floor hardener, powder-like, silica based, material is available by way of example from the Euclid Chemical Co., 19218 Redwood Road, Cleveland, Oh. 44110. Therefore, the same industrial job may require spreading, for example, one-half inch trap rock for one purpose as well as spreading the powder-like light reflecting and floor hardening material in other areas of the same job. Conventional spreaders have not readily adapted to this wide range of particulate size.
In another aspect of using prior art material spreaders on industrial jobs is the fact that as the use of such spreaders has increased, the quantity of material spread and thus the amount of power required to dispense the material from the hoppers has become a major consideration. The present invention recognizes that in prior art spreaders where the dispensing cylinder with vanes is located directly below the hopper load of material the vanes are necessarily lifting material during part of the cylinder rotation. This mode of operation consumes substantial power. Additionally, for many industrial and other job requirements it has become necessary to substantially improve the smoothness of the surface of spread material to eliminate or at least substantially reduce the so-called "washboard effect" in spread material inherent to prior art spreaders.
With the foregoing in mind, the object of the present invention is that of providing a spreader adapted to handle a wide range of particulate material ranging, for example, from relatively large size rock to powder-like material, a spreader inherently able to spread the material so as to achieve a smoother surface than has been achieved with prior art spreaders to eliminate or at least substantially reduce the so-called washboard effect, a spreader which in operation requires substantially less power to dispense the material than has been required with prior art spreaders and finally a spreader adapted for use either on a conventional bridge spanning the area to be covered or without a bridge where a single hopper spans the area to be covered as, for example, in spreading rock for highway application. The foregoing and other objects will become apparent as the description proceeds.